An unusually long and large flight restriction has been placed on the Chicago area for several days, a move officials say was sparked by a "credible threat" of attacks on law enforcement. The Federal Aviation Administration confirmed a temporary flight restriction was put in place “at the request of the Department of Homeland Security." The restrictions include aircraft from the surface to 400 feet, citing "security reasons." The restricted zone extends in a 15-nautical-mile radius stretching from downtown Chicago to north of Evanston, west of Elmhurst and south of Dolton. "Pilots who do not adhere to the following [procedures] may...